The main by-products of waste incineration include bottom ash which is released directly from the incinerator furnace and fly ash which is collected in the boiler hoppers and from the hoppers of the air pollution control equipment associated with an incinerator or power generation system. With increasing emphasis being placed on providing better air pollution control of incinerator and power generator plant emissions, most, if not all, incineration and power generation systems utilize air pollution control equipment that injects alkalis into a plant's various gas passages and/or combustion zones. As a result, the reacted and unreacted alkalis remain in the ash and particularly in the fly ash.
The unreacted alkalis cause the combustion by-products to exhibit varying degrees of hygroscopicity when the material is quenched. Following quenching, the combined ash often exhibits significant free water run-off or in extreme situations may coat downstream equipment. The water run-off is problematic for downstream conveyors since expensive additional equipment is needed to collect the excess water. Additionally, the relatively wet condition of the material also adversely affects the downstream recovery of ferrous scrap from the waste stream. More critically, the free water run-off increases the potential for pollution resulting from the leaching of toxins contained in the ash into the ground water and aquifers at the disposal sites.
Although a number of treatments for stabilizing combined ash have been proposed, none exist that substantially dewater the combined ash efficiently, quickly and economically without the use of expensive plant equipment, chemical fixation agents or complex mechanical treating devices. Moreover, an apparatus does not exist that takes advantage of pre-existing equipment and that achieves substantial results while making only minor modifications to such equipment.